Lettuce variety 41-cr2537 rz

ABSTRACT

The present invention relates to a Lactuca sativa seed designated 41-CR2537 RZ. The present invention also relates to a Lactuca sativa plant produced by growing the 41-CR2537 RZ seed. The invention further relates to methods for producing the lettuce cultivar, represented by lettuce variety 41-CR2537 RZ.

INCORPORATION BY REFERENCE

This application claims priority to U.S. provisional patent applicationSer. No. 63/249,092 filed 28 Sep. 2021.

The foregoing applications, and all documents cited therein or duringtheir prosecution (“appln cited documents”) and all documents cited orreferenced in the application cited documents, and all documents citedor referenced herein (“herein cited documents”), and all documents citedor referenced in herein cited documents, together with anymanufacturer's instructions, descriptions, product specifications, andproduct sheets for any products mentioned herein or in any documentincorporated by reference herein, are hereby incorporated herein byreference, and may be employed in the practice of the invention. Morespecifically, all referenced documents are incorporated by reference tothe same extent as if each individual document was specifically andindividually indicated to be incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a new lettuce (Lactuca sativa) varietydesignated 41-CR2537 RZ. Lettuce variety 41-CR2537 RZ exhibits acombination of traits including resistance to downy mildew (Bremialactucae) races B1:16EU to B1:37EU, and B1:1US to B1:9US, resistance tocurrant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0, a small plantdiameter and leaves with solid main veins.

BACKGROUND OF THE INVENTION

All cultivated forms of lettuce belong to the highly polymorphicspecies, Lactuca sativa, which is grown for its edible head and leaves.As a crop, lettuces are grown commercially wherever environmentalconditions permit the production of an economically viable yield.

Lactuca sativa is in the Cichoreae tribe of the Asteraceae (Compositae)family. Lettuce is related to chicory, sunflower, aster, scorzonera,dandelion, artichoke and chrysanthemum. Sativa is one of about 300species in the genus Lactuca.

Lettuce cultivars are susceptible to a number of pests and diseases suchas downy mildew (Bremia lactucae). Every year this disease leads tomillions of dollars of lost lettuce crop throughout the world. Downymildew (Bremia lactucae) is highly destructive on lettuce grown atrelatively low temperature and high humidity. Downy mildew is caused bya fungus, Bremia lactucae, which can be one of the following strains:B1:16EU, B1:17EU, B1:18EU, B1:20EU, B1:21EU, B1:22EU, B1:23EU, B1:24EU,B1:25EU, B1:26EU, B1:27EU, B1:29EU, B1:30EU, B1:31EU, B1:32EU, B1:33EU,B1:34EU, B1:35EU, B1:36EU (Van Ettekoven, K. et al., “Identification anddenomination of ‘new’ races of Bremia lactucae,” In: Lebeda, A. andKristkova, E (eds.), Eucarpia Leafy Vegetables, 1999, PalackyUniversity, Olomouc, Czech Republic, pp. 171-175; Van der Arend et al.“Identification and denomination of “new” races of Bremia lactucae inEurope by IBEB until 2002.” In: Van Hintum, Th et al. (eds.), EucarpiaLeafy Vegetables Conference 2003, Centre for Genetic Resources,Wageningen, The Netherlands, p. 151; Plantum N L (Dutch association forbreeding, tissue culture, production and trade of seeds and youngplants), Van der Arend et al. “Identification and denomination of “new”races of Bremia lactucae in Europe by IBEB until 2002.” In: Van Hintum,Th et al. (eds.), Eucarpia Leafy Vegetables Conference 2003, Centre forGenetic Resources, Wageningen, The Netherlands, p. 151; Plantum N L(Dutch association for breeding, tissue culture, production and trade ofseeds and young plants); IBEB press release: “New race of Bremialactucae B1:27 identified and nominated”, May 2010; Plantum N L, IBEBpress release: “New races of Bremia lactucae, B1:29, B1:30 and B1:31identified and nominated”, August 2013; Plantum N L, IBEB press release:“A new race of Bremia lactucae, B1:32 identified and nominated inEurope”, May 2015, Plantum N L, IBEB-EU press release: “A new race ofBremia lactucae, B1:33EU identified and denominated in Europe”, May2017; Plantum N L, IBEB-EU press release: “Two new races of Bremialactucae, B1:34EU and B1:35EU identified and nominated in Europe”, July2018; Plantum N L, IBEB-EU press release: “A new race of Bremialactucae, B1:36EU identified and denominated in Europe”, July 2019,Plantum N L, IBEB-EU press release: “A new race of Bremia lactucae,B1:37EU identified and denominated in Europe”, June 2021; Plantum N L),B1:1US, B1:2US, B1:3US, B1:4US, B1:5US, B1:6US, B1:7US, B1:8US, B1:9US(Schettini, T. M., Legg, E. J., Michelmore, R. W., 1991. Insensitivityto metalaxyl in California populations of Bremia lactucae and resistanceof California lettuce cultivars to downy mildew. Phytopathology 81(1).p. 64-70; Michelmore R. & Ochoa. 0. “Breeding Crisphead Lettuce” In:California Lettuce Research Board, Annual Report 2005-2006, 2006,Salinas, Calif., pp. 55-68; http://bremia.ucdavis.edu/data/B1_9 US.pdf).

Downy mildew causes pale, angular, yellow areas bounded by veins on theupper leaf surfaces. Sporulation occurs on the opposite surface of theleaves. The lesions eventually turn brown, and they may enlarge andcoalesce. These symptoms typically occur first on the lower leaves ofthe lettuce, but under ideal conditions may move into the upper leavesof the head. When the fungus progresses to this degree, the head cannotbe harvested. Less severe damage requires the removal of more leavesthan usual, especially when the lettuce reaches its final destination.

Of the various species of aphids that feed on lettuce, thecurrant-lettuce aphid (Nasonovia ribisnigri) is the most destructivespecies because it feeds both on the leaves of the lettuce as well asthe heart of the lettuce, making it difficult to control withconventional insecticides. The lettuce aphid feeds by sucking sap fromthe lettuce leaves. Although direct damage to the lettuce may belimited, its infestation has serious consequences because the presenceof aphids makes lettuce unacceptable to consumers.

Fusarium root rot (wilt) of lettuce, caused by the soil borne fungusFusarium oxysporum f. sp. lactucae, is an important disease of lettucein warmer growing areas. It is found in the lettuce winter productionareas of Arizona and California, and causes significant damage in theearly plantings. In recent years, Fusarium root rot has also spread tothe summer production area of the Salinas Valley. The fungus maypenetrate plants through natural apertures or via wounds on the roots.Transmission of Fusarium oxysporum f. sp. lactucae may occur throughinfected seeds, infected transplants, or spread by soil as spores mayremain viable in soil for long periods of time. Affected plants exhibitleaf yellowing and wilting. Crown tissue and upper roots display signsof reddish brown necrosis, followed by decaying. Leaf veins may alsoshow vascular necrosis. Infected plants are stunted and often die,resulting in significant crop losses, and unmarketable product. Fusariumroot rot can be prevented by soil sterilisation, however, this is anexpensive process.

Crunchy lettuce is a new type of lettuce which has the thick inner andouter leaves that provide a crisp and crunchy bite, and it has the leafand oval head shape of Cos lettuce. Crunchy lettuce is particularlysuitable for mechanical harvesting of whole heads or single leaves. Itshould provide an attractive product at harvestable stage which isaccepted by consumers and/or the processing industry.

There are certain constraints that make lettuce varieties more fit orless fit for mechanical harvesting.

One constraint is caused by the use of mechanically-driven horizontalknives that easily damage the hollow main veins of leaves and cuthalfway through the prostrate, round-shaped, lower outer leaves, whichresults in wide cut surfaces. Cutting damage on a leaf with a hollowmain vein is often not restricted to the cut surface but bruisingextends into the leaf along the main vein.

Another constraint is the requirement for a leaf to have a good shelflife. This means that the leaves should get through the washing anddrying process in the factory without bruising or breaking. The leavesshould be sufficiently thick and tough to avoid wilting.

The oval shape of the leaves and the very thick main veins of crunchylettuce make it particularly suitable for mechanical harvesting.

For the purpose of whole head and heart production, it is important thatthe leaves are wide enough to overlap and maintain head integrity. Shortcore internodes and petioles give a closed base. A longer core internodecan be compensated by a more erect leaf attitude, that causes the baseto be closed. The closed base and overlapplng head leaves reduce theproduct surface, resulting in less wilting and a longer shelf life. Thisis desired by traders, retailers, and consumers.

Citation or identification of any document in this application is not anadmission that such document is available as prior art to the presentinvention.

SUMMARY OF THE INVENTION

Given the need expressed by relevant stakeholders for a lettuce varietywhich shows a combination of traits including resistance to downy mildew(Bremia lactucae) races B1:16EU to B1:37EU, and B1:1US to B1:9US,resistance to currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,a small plant diameter and leaves with solid main veins, the presentinvention addresses this need by providing a new type of lettuce(Lactuca sativa) variety, designated 41-CR2537 RZ.

The present invention provides a new lettuce (Lactuca sativa) varietydesignated 41-CR2537 RZ. This new lettuce variety exhibits a combinationof traits including resistance to downy mildew (Bremia lactucae) racesB1:16EU to B1:37EU, and B1:1US to B1:9US, resistance to currant-lettuceaphid (Nasonovia ribisnigri) biotype Nr:0, a small plant diameter andleaves with solid main veins.

The present invention provides seed of a lettuce (Lactuca sativa)variety designated 41-CR2537 RZ. A sample of seeds of said lettucevariety, have been deposited with the National Collections ofIndustrial, Marine and Food Bacteria (NCIMB) in Bucksburn, Aberdeen AB219YA, Scotland, UK and have been assigned NCIMB Accession No. 44003.

In one embodiment, the invention provides a lettuce plant grown from theseed of lettuce (Lactuca sativa) variety 41-CR2537 RZ.

In another embodiment, the invention provides a lettuce plant designated41-CR2537 RZ, which is a plant grown from seed having been depositedunder NCIMB Accession No. 44003.

In one embodiment, the invention provides for a lettuce plant which maycomprise genetic information for exhibiting all of the physiological andmorphological characteristics of a plant of the invention, wherein thegenetic information is as contained in a plant, a sample of seed of saidvariety having been deposited under NCIMB Accession No. 44003.

In one embodiment, the invention provides for a lettuce plant exhibitingall the physiological and morphological characteristics of a plant ofthe invention, and having the genetic information for so exhibiting thecombination of traits, wherein the genetic information is as containedin a plant, a sample of seed of said variety having been deposited underNCIMB Accession No. 44003.

In an embodiment of the present invention, there also is provided partsof a lettuce plant of the invention, which may include parts of alettuce plant exhibiting all the physiological and morphologicalcharacteristics of a plant of the invention, or parts of a lettuce planthaving any of the mentioned resistance(s) and a combination of traitsincluding one or more or all morphological and physiologicalcharacteristics tabulated herein, including parts of lettuce variety41-CR2537 RZ, wherein the plant parts are involved in sexualreproduction, which include, without limitation, microspores, pollen,ovaries, ovules, embryo sacs or egg cells and/or wherein the plant partsare suitable for vegetative reproduction, which include, withoutlimitation, cuttings, roots, stems, cells or protoplasts and/or whereinthe plant parts are tissue culture of regenerable cells in which thecells or protoplasts of the tissue culture are derived from a tissuesuch as, for example and without limitation, leaves, pollen, embryos,cotyledon, hypocotyls, meristematic cells, roots, root tips, anthers,flowers, seeds or stems. The plants of the invention from which suchparts may come from include those wherein a sample of seed of whichhaving been deposited under NCIMB Accession No. 44003 or lettuce varietyor cultivar designated 41-CR2537 RZ, as well as seed from such a plant,plant parts of such a plant (such as those mentioned herein) and plantsfrom such seed and/or progeny of such a plant, advantageously progenyexhibiting such combination of such traits, each of which, is within thescope of the invention; and such combination of traits.

In a further embodiment there is a plant regenerated from theabove-described plant parts or regenerated from the above-describedtissue culture. Advantageously such a plant may have morphologicaland/or physiological characteristics of lettuce variety 41-CR2537 RZand/or of a plant grown from seed, a sample of seed of which having beendeposited under NCIMB Accession No. 44003— including without limitationsuch plants having all of the physiological and morphologicalcharacteristics of lettuce variety 41-CR2537 RZ and/or of a plant grownfrom seed, a sample of seed of which having been deposited under NCIMBAccession No. 44003.

Accordingly, in still a further embodiment, there is provided a lettuceplant having all of the physiological and morphological characteristicsof lettuce variety 41-CR2537 RZ, a sample of seed of which having beendeposited under NCIMB Accession No. 44003. Such a plant may be grownfrom the seeds, regenerated from the above-described plant parts, orregenerated from the above-described tissue culture. A lettuce planthaving any of the aforementioned resistance(s), and one or moremorphological or physiological characteristics recited or tabulatedherein, and a lettuce plant advantageously having all of theaforementioned resistances and the characteristics recited and tabulatedherein, are preferred. Parts of such plants—such as those plant partsabove-mentioned—are encompassed by the invention.

In a further aspect, the invention provides a method of vegetativelypropagating a plant of lettuce variety 41-CR2537 RZ which may comprise(a) collecting tissue capable of being propagated from a plant oflettuce 41-CR2537 RZ, a sample of seed of said variety having beendeposited under NCIMB accession No. 44003 and (b) cultivating the tissueto obtain proliferated shoots and rooting the proliferated shoots toobtain rooted plantlets. Optionally the invention further may comprisegrowing plants from the rooted plantlets. Plantlets and plants producedby these methods, are encompassed by the invention.

In one embodiment, there is provided a method for producing a progeny oflettuce cultivar 41-CR2537 RZ which may comprise crossing a plantdesignated 41-CR2537 RZ with itself or with another lettuce plant,harvesting the resultant seed, and growing said seed.

In a further embodiment, a progeny plant is provided which is producedby this method, wherein said progeny exhibits a combination of traitsincluding resistance to downy mildew (Bremia lactucae) races B1:16EU toB1:37EU, and B1:1US to B1:9US, resistance to currant-lettuce aphid(Nasonovia ribisnigri) biotype Nr:0, a small plant diameter and leaveswith solid main veins.

In another embodiment, a progeny plant is provided which is produced bythe above method, wherein said progeny exhibits all the morphologicaland physiological characteristics of the lettuce variety designated41-CR2537 RZ, a sample of seed of said variety having been depositedunder NCIMB accession No. 44003.

In a further embodiment there is provided a progeny plant produced bysexual or vegetative reproduction, grown from seeds, regenerated fromthe above-described plant parts, or regenerated from the above-describedtissue culture of the lettuce cultivar or a progeny plant thereof, asample of seed of which having been deposited under NCIMB Accession No.44003. The progeny may have any of the aforementioned resistance(s), andone or more morphological or physiological characteristics recited ortabulated herein, and a progeny plant advantageously having all of theaforementioned resistances and the characteristics recited and tabulatedherein, are preferred.

Progeny of the lettuce variety 41-CR2537 RZ may be modified in one ormore other characteristics, in which the modification is a result of,for example and without limitation, mutagenesis or transformation with atransgene.

In still another embodiment, the present invention provides progeny oflettuce cultivar 41-CR2537 RZ produced by sexual or vegetativereproduction, grown from seed, regenerated from the above-describedplant parts, or regenerated from the above-described tissue culture ofthe lettuce cultivar or a progeny plant thereof.

The invention further relates to a method for producing a seed of a41-CR2537 RZ-derived lettuce plant which may comprise (a) crossing aplant of lettuce variety 41-CR2537 RZ, a sample of seed of which havingbeen deposited under NCIMB Accession No. 44003, with a second lettuceplant, and (b) whereby seed of a 41-CR2537 RZ-derived lettuce plantforms. This method may further comprise (c) crossing a plant grown from41-CR2537 RZ-derived lettuce seed with itself or with a second lettuceplant to yield additional 41-CR2537 RZ-derived lettuce seed, (d) growingthe additional 41-CR2537 RZ-derived lettuce seed of step (c) to yieldadditional 41-CR2537 RZ-derived lettuce plants, and (e) repeating thecrossing and growing of steps (c) and (d) for an additional 3-10generations to generate further 41-CR2537 RZ-derived lettuce plants, and(f) whereby seed of a 41-CR2537 RZ-derived lettuce plant forms. A seedproduced by this method and a plant grown from said seed also form partof the invention.

The invention also relates to a method of introducing at least one newtrait into a plant of lettuce variety 41-CR2537 RZ which may comprise:(a) crossing a plant of lettuce variety 41-CR2537 RZ, a sample of seedof which having been deposited under NCIMB Accession No. 44003, with asecond lettuce plant that may comprise at least one new trait to produceprogeny seed, (b) harvesting and planting the progeny seed to produce atleast one progeny plant of a subsequent generation, wherein the progenyplant may comprise the at least one new trait, (c) crossing the progenyplant with a plant of lettuce variety 41-CR2537 RZ to produce backcrossprogeny seed, (d) harvesting and planting the backcross progeny seed toproduce a backcross progeny plant, and (e) repeating steps (c) and (d)for at least three additional generations to produce a lettuce plant ofvariety 41-CR2537 RZ which may comprise at least one new trait and allof the physiological and morphological characteristics of a plant oflettuce variety 41-CR2537 RZ, when grown in the same environmentalconditions. A lettuce plant produced by this method also forms part ofthe invention.

Mutations can be introduced randomly by means of one or more chemicalcompounds, such as ethyl methane sulphonate (EMS), nitrosomethylurea,hydroxylamine, proflavine, N-methly-N-nitrosoguanidine,N-ethyl-N-nitrosourea, N-methyl-N-nitro-nitrosoguanidine, diethylsulphate, ethylene imine, sodium azide, formaline, urethane, phenol andethylene oxide, and/or by physical means, such as UV-irradiation, fastneutron exposure, X-rays, gamma irradiation, and/or by insertion ofgenetic elements, such as transposons, T-DNA, retroviral elements.

Mutations can also be introduced by more specific, targeted introductionof at least one modification by means of homologous recombination,oligonucleotide-based mutation introduction, zinc-finger nucleases(ZFN), transcription activator-like effector nucleases (TALENs) orClustered Regularly Interspaced Short Palindromic Repeat (CRISPR)systems.

The invention further relates to a method of producing a plant oflettuce variety 41-CR2537 RZ which may comprise at least one new trait,the method which may comprise introducing a mutation or transgeneconferring the at least one new trait into a plant of lettuce variety41-CR2537 RZ, wherein a sample of seed of said variety has beendeposited under NCIMB Accession No. 44003. A lettuce plant produced bythis method also forms part of the invention.

In still a further embodiment, the invention provides a method ofproducing a lettuce seed which may comprise crossing a male parentlettuce plant with a female parent lettuce plant and harvesting theresultant lettuce seed, in which the male parent lettuce plant or thefemale parent lettuce plant is a lettuce plant of the invention, e.g. alettuce plant having all of the morphological or physiologicalcharacteristics tabulated herein, including a lettuce plant of lettucecultivar 41-CR2537 RZ, a sample of seed of which having been depositedunder. The resultant lettuce seed produced by this method and thelettuce plant that is produced by growing said lettuce seed also formspart of the invention.

In still a further embodiment, the invention provides a method ofproducing a lettuce cultivar which exhibits all of the physiological andmorphological characteristics of lettuce variety 41-CR2537 RZ, a sampleof seed of said variety having been deposited under NCIMB accession No.44003.

The invention even further relates to a method of producing lettuceleaves as a food product which may comprise: (a) sowing a seed oflettuce variety 41-CR2537 RZ, a sample of seed of which having beendeposited under NCIMB Accession No. 44003, (b) growing said seed into aharvestable lettuce plant and (c) harvesting lettuce leaves or headsfrom the plant. The invention further comprehends packaging and/orprocessing the lettuce plants, heads or leaves.

Also encompassed by the invention is a container which may comprise oneor more lettuce plants of the invention for harvest of leaves.

Further encompassed by the invention is a method of determining thegenotype of a plant of lettuce variety 41-CR2537 RZ, a sample of seed ofwhich has been deposited under NCIMB Accession No. 44003, or a firstgeneration progeny thereof, which may comprise obtaining a sample ofnucleic acids from said plant and comparing said nucleic acids to asample of nucleic acids obtained from a reference plant, and detecting aplurality of polymorphisms between the two nucleic acid samples, whereinthe plurality of polymorphisms are indicative of lettuce variety41-CR2537 RZ and/or give rise to the expression of any one or more, orall, of the physiological and morphological characteristics of lettucevariety 41-CR2537 RZ of the invention.

Accordingly, it is an object of the invention to not encompass withinthe invention any previously known product, process of making theproduct, or method of using the product such that Applicants reserve theright and hereby disclose a disclaimer of any previously known product,process, or method. It is further noted that the invention does notintend to encompass within the scope of the invention any product,process, or making of the product or method of using the product, whichdoes not meet the written description and enablement requirements of theUSPTO (35 U.S.C. § 112, first paragraph), such that Applicants reservethe right and hereby disclose a disclaimer of any previously describedproduct, process of making the product, or method of using the product.

It is noted that in this disclosure and particularly in the claims,terms such as “comprises”, “comprised”, and “comprising” and the like(e.g., “includes”, “included”, “including”, “contains”, “contained”,“containing”, “has”, “had”, “having”, etc.) can have the meaningascribed to them in US Patent law, i.e., they are open ended terms. Forexample, any method that “comprises,” “has” or “includes” one or moresteps is not limited to possessing only those one or more steps and alsocovers other unlisted steps. Similarly, any plant that “comprises,”“has” or “includes” one or more traits is not limited to possessing onlythose one or more traits and covers other unlisted traits. Similarly,the terms “consists essentially of” and “consisting essentially of” havethe meaning ascribed to them in US Patent law, e.g., they allow forelements not explicitly recited, but exclude elements that are found inthe prior art or that affect a basic or novel characteristic of theinvention. See also MPEP § 2111.03. In addition, the term “about” isused to indicate that a value includes the standard deviation of errorfor the device or method being employed to determine the value.

These and other embodiments are disclosed or are obvious from andencompassed by the following Detailed Description.

Deposit

The Deposit with NCIMB Ltd, Ferguson Building, Craibstone Estate,Bucksburn, Aberdeen AB21 9YA, UK, on 25 Jul. 2022, under depositaccession number NCIMB 44003 was made and accepted pursuant to the termsof the Budapest Treaty. Upon issuance of a patent, all restrictions uponthe deposit will be removed, and the deposit is intended to meet therequirements of 37 CFR §§ 1.801-1.809. The deposit will be irrevocablyand without restriction or condition released to the public upon theissuance of a patent and for the enforceable life of the patent. Thedeposit will be maintained in the depository for a period of 30 years,or 5 years after the last request, or for the effective life of thepatent, whichever is longer, and will be replaced if necessary duringthat period.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, but notintended to limit the invention solely to the specific embodimentsdescribed, may best be understood in conjunction with the accompanyingdrawing, in which:

FIG. 1 is an illustration of six different shapes of the fourth leaffrom a 20-day old seedling grown under optimal conditions.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides methods and compositions relating to plants,seeds and derivatives of a new lettuce variety herein referred to aslettuce variety 41-CR2537 RZ. Lettuce variety 41-CR2537 RZ is a uniformand stable line, distinct from other such lines.

In a preferred embodiment, the specific type of breeding method employedfor developing a lettuce cultivar is pedigree selection, where bothsingle plant selection and mass selection practices are employed.Pedigree selection, also known as the “Vilmorin system of selection,” isdescribed in Fehr, W., Principles of Cultivar Development, Volume I,MacMillan Publishing Co., which is hereby incorporated by reference.

When pedigree selection is applied, in general selection is firstpracticed among F₂ plants. In the next season, the most desirable F₃lines are first identified, and then desirable F₃ plants within eachline are selected. The following season and in all subsequentgenerations of inbreeding, the most desirable families are identifiedfirst, then desirable lines within the selected families are chosen, andfinally desirable plants within selected lines are harvestedindividually. A family refers to lines that were derived from plantsselected from the same progeny from the preceding generation.

Using this pedigree method, two parents may be crossed using anemasculated female and a pollen donor (male) to produce F₁ offspring.Lettuce is an obligate self-pollination species, which means that pollenis shed before stigma emergence, assuring 100% self-fertilization.Therefore, in order to optimize crossing, a method of misting may beused to wash the pollen off prior to fertilization to assure crossing orhybridization.

Parental varieties are selected from commercial varieties thatindividually exhibit one or more desired phenotypes. Additionally, anybreeding method involving selection of plants for the desired phenotypemay be used in the method of the present invention.

The F₁ may be self-pollinated to produce a segregating F₂ generation.Individual plants may then be selected which represent the desiredphenotype in each generation (F₃, F₄, F₅, etc.) until the traits arehomozygous or fixed within a breeding population.

A detailed description of the development of lettuce variety 41-CR2537RZ is described in Table 1. The seedlot in year 6, seedlot 20R.404, wasdeposited with the NCIMB under deposit number NCIMB 44003.

TABLE 1 Year Description Location 0 Final F1-cross plant in glasshouse.Fijnaart, The Netherlands 0-1 F1 plant grown for F2 seed production inFijnaart, The glasshouse. Netherlands 2-3 F2 plant selected in openfield, followed Fijnaart, The by F3 seed production. Netherlands 3-4 F3plant selected in open field, followed Fijnaart, The by F4 seedproduction. Netherlands 4-5 F4 plant selected in open field, followedFijnaart, The by F5 seed production. Netherlands 5-6 F5 plant selectedin open field, followed Fijnaart, The byF6 seed production. Netherlands6 F6 line established uniform, multiplied in Daylesford, plastic tunnel;seed lot 20R.404. Australia

In one embodiment, a plant of the invention has all the physiologicaland morphological characteristics of lettuce variety 41-CR2537 RZ. Thesecharacteristics of a lettuce plant of the invention, e.g. variety41-CR2537 RZ, are summarized in Table 2.

Next to the physiological and morphological characteristics mentioned inTable 2, a plant of the invention also exhibits resistance to downymildew (Bremia lactucae Regel.) races B1:16EU to B1:37EU and B1:1US toB1:9US.

As used herein resistance against Bremia lactucae is defined as theability of a plant to resist infection by each of the various strainsB1:16EU to B1:37EU, B1:1US to B1:9US of Bremia lactucae Regel. in allstages between the seedling stage and the harvestable plant stage.B1:16EU to B1:36EU means strains B1:16EU, B1:17EU, B1:18EU, B1:20EU,B1:21EU, B1:22EU, B1:23EU, B1:24EU, B1:25EU, B1:26EU, B1:27EU, B1:29EU,B1:30EU, B1:31EU, B1:32EU, B1:33EU, B1:34EU, B1:35EU, B1:36EU, B1:37EU(Van Ettekoven K, Van der Arend AJM, 1999. identification anddenomination of ‘new’ races of Bremia lactucae. In: Lebeda A, KristkovaE (eds.) Eucarpia leafy vegetables ‘99. Palacky University, Olomouc,Czech Republic, 1999: 171-175; Van der Arend, A. J. M., Gautier, J.,Guenard, M., Michel, H., Moreau, B., de Ruijter, J., Schut, J. W. and deWitte, I. (2003). Identification and denomination of ‘new’ races ofBremia lactucae in Europe by IBEB until 2002. In: Eucarpia leafyvegetables 2003. Proceedings of the Eucarpia Meeting on leafy vegetablesgenetics and breeding. Noorwijkerhout, The Netherlands. Eds. Van HintumT., Lebeda A., Pink D., Schut J. pp 151-160; Van der Arend AJM, GautierJ, Grimault V, Kraan P, Van der Laan R, Mazet J, Michel H, Schut J W,Smilde D, De Witte I (2006) Identification and denomination of “new”races of Bremia lactucae in Europe by IBEB until 2006; incorporatedherein by reference; Plantum N L (Dutch association for breeding, tissueculture, production and trade of seeds and young plants), IBEB pressrelease, “New race of Bremia lactucae B1:27 identified and nominated”,May 2010; Plantum N L, IBEB press release, “New races of Bremialactucae, B1:29, B1:30 and B1:31 identified and nominated”, August 2013;Plantum N L, IBEB press release, “A new race of Bremia lactucae, B1:32identified and nominated in Europe”, May 2015; Plantum N L, IBEB-EUpress release, “A new race of Bremia lactucae, B1:33EU identified anddenominated in Europe”, May 2017; Plantum N L, IBEB-EU press release,“Two new races of Bremia lactucae, B1:34EU and B1:35EU identified andnominated in Europe”, July 2018; Plantum N L, IBEB-EU press release, “Anew race of Bremia lactucae, B1:36EU identified and denominated inEurope”, July 2019, IBEB-EU press release: “A new race of Bremialactucae, B1:37EU identified and denominated in Europe”, June 2021;Plantum N L); B1:1US to B1:9US means B1:1US, B1:2US, B1:3US, B1:4US,B1:5US, B1:6US, B1:7US, B1:8US, B1:9US (Schettini, T. M., Legg, E. J.,Michelmore, R. W., 1991. Insensitivity to metalaxyl in Californiapopulations of Bremia lactucae and resistance of California lettucecultivars to downy mildew, Phytopathology 81(1). p.64-′70; Michelmore R.& Ochoa. 0. “Breeding Crisphead Lettuce.” In: California LettuceResearch Board, Annual Report 2005-2006, 2006, Salinas, Calif., pp.55-68; http://bremia.ucdavis.edu/data/B1_9US.pdf).

Resistance typically is tested by two interchangeable methods, describedby Bonnier, F. J. M. et al. (Euphytica, 61(3):203-211, 1992;incorporated herein by reference). One method involves inoculating 7-dayold seedlings, and observing sporulation 10 to 14 days later. The othermethod involves inoculating leaf discs with a diameter of 18 mm obtainedfrom a non-senescent, fully grown true leaf and observing sporulation 10days later.

As used herein, resistance against Nasonovia ribisnigri (Mosley), orcurrant-lettuce aphid, is defined as the plant characteristic whichresults in a non-feeding response of the aphid on the leaves of theplant in all stages between 5 true-leaf stage and harvestable plantstage (U.S. Pat. No. 5,977,443 to Jansen, J. P. A., “Aphid Resistance inComposites,” p. 12, 1999; incorporated herein by reference).

Resistance is tested by spreading at least ten aphids of biotype Nr:0 ona plant in a plant stage between 5 true leaves and harvestable stage,and observing the density of the aphid population on the plant as wellas the growth reduction after 14 days in a greenhouse, with temperaturesettings of 23 degrees Celsius in daytime and 21 degrees Celsius atnight. Day length is kept at 18 hours by assimilation lights.

As used herein, resistance against Fusarium oxysporum f. sp. lactucae,is defined as the ability of a plant to resist infection by race Fol:1.Resistance may be tested by two interchangeable methods. One method isdescribed by Hubbard and Gerik (1993, Plant Disease 77(7): 750-754;incorporated herein by reference). The other test is described byTsuchiya et al., (2004, J. Japan. Soc. Hort. Sci 73(2): 105-113;incorporated herein by reference).

As used herein, Crunchy lettuce is a new lettuce type, which has an ovalhead and leaf shape and very thick outer and inner leaves. The plantdevelops in an upright growing habit with thick, long and green,non-flabellate leaves. The younger leaves are longer than they are wide,cupping together to form an elongated loose head. Leaf margins areentire. Outer leaves range in color from light green to dark green.Inner heartleaves are smaller and range from light yellow to light greenin color.

As used herein, a solid main vein is the main vein of a fully-growntenth to fifteenth leaf, which is characterized by the fact that thevein is not hollow, which is observed by visual inspection of atransverse section of the leaf. The transverse section should be made at40% of the total leaf length, starting from the leaf base. Forcomparison a standard variety can be used: Crunchita R Z, with hollowmain veins. The lettuce variety 41-CR2537 RZ has solid main veins. Solidmain veins are also sometimes defined as solid ribs.

Embodiments of the inventions advantageously have one or more, and mostadvantageously all, of these characteristics.

In Table 2, the characteristics of “41-CR2537 RZ” are shown.

TABLE 2 SEED Seed Color White PLANT Plant: Head Diameter Small Plant:Degree of Overlapping of Upper medium Part of Leaves LEAF Leaf: LeafAttitude Erect to Semi- Erect Leaf: Number of Divisions Absent or veryfew Leaf: Shape Oblanceolate to Obovate Leaf: Shape of Apex RoundedLeaf: Longitudinal Section Flat Leaf: Anthocyanin Coloration Absent orVery Weak Leaf: Color Green Leaf: Intensity of Green Color Medium Leaf:Glossiness of Upper Side Very weak to weak Leaf Thickness Thick Leaf:Blistering Very weak to weak Leaf: Size of Blisters Very small to smallLeaf: Undulation of Margin Very Weak to Weak Leaf: Type of Incisions ofMargin Crenate Leaf: Depth of Incisions of Margin Very Shallow toShallow Leaf: Density of Incisions of Margin Sparse to Medium Leaf:Venation Not Flabellate HEAD Head: Size Small Head: Shape inLongitudinal Section Narrow Elliptic Head: Density Medium to DenseHARVEST Time of Harvest Maturity (Only varieties Very Late with Degreeof Overlapping of Upper Part of Leaves) BOLTING Bolting: Time ofBeginning of Bolting Very Late Auxilliary Sprouting Absent or WeakBolting: Bolting Stem: Fasciation Very Weak to Weak PLANT TYPE PlantType Cos or Romaine COTYLEDON TO FOURTH LEAF STAGE Shape of CotyledonsIntermediate Shape of Fourth Leaf Elongated PLANT Plant head Diameter 11cm Plant Spread of Frame Leaves 25 cm BUTT Butt: Shape Rounded Butt:Midrib Moderately Raised HARVEST MATURITY Time of harvest Maturity (Onlyvarieties 98 days with Degree of Overlapping of Upper part of leaves:medium or Strong) (Days)

In one aspect the invention provides a new type of lettuce (Lactucasativa) variety, designated 41-CR2537 RZ. Lettuce cultivar 41-CR2537 RZexhibits a combination of traits including resistance to downy mildew(Bremia lactucae) races B1:16EU to B1:37EU, and B1:1US to B1:9US,resistance to currant-lettuce aphid (Nasonovia ribisnigri) biotype Nr:0,a small plant diameter and leaves with solid main veins.

In an embodiment, the invention relates to lettuce plants that have allthe physiological and morphological characteristics of the invention andhave acquired said characteristics by introduction of the geneticinformation that is responsible for the characteristics from a suitablesource, either by conventional breeding, or genetic modification, inparticular by cisgenesis or transgenesis. Cisgenesis is geneticmodification of plants with a natural gene, coding for an (agricultural)trait, from the crop plant itself or from a sexually compatible donorplant. Transgenesis is genetic modification of a plant with a gene froma non-crossable species or a synthetic gene.

Just as useful traits that may be introduced by backcrossing, usefultraits may be introduced directly into the plant of the invention, beinga plant of lettuce variety 41-CR2537 RZ, by genetic transformationtechniques; and, such plants of lettuce variety 41-CR2537 RZ that haveadditional genetic information introduced into the genome or thatexpress additional traits by having the DNA coding there for introducedinto the genome via transformation techniques, are within the ambit ofthe invention, as well as uses of such plants, and the making of suchplants.

Genetic transformation may therefore be used to insert a selectedtransgene into the plant of the invention, being a plant of lettucevariety 41-CR2537 RZ or may, alternatively, be used for the preparationof transgenes which may be introduced by backcrossing. Methods for thetransformation of plants, including lettuce, are well known to those ofskill in the art.

Vectors used for the transformation of lettuce cells are not limited solong as the vector may express an inserted DNA in the cells. Forexample, vectors which may comprise promoters for constitutive geneexpression in lettuce cells (e.g., cauliflower mosaic virus 35Spromoter) and promoters inducible by exogenous stimuli may be used.Examples of suitable vectors include pBI binary vector. The “lettucecell” into which the vector is to be introduced includes various formsof lettuce cells, such as cultured cell suspensions, protoplasts, leafsections, and callus. A vector may be introduced into lettuce cells byknown methods, such as the polyethylene glycol method, polycationmethod, electroporation, Agrobacterium-mediated transfer, particlebombardment and direct DNA uptake by protoplasts. To effecttransformation by electroporation, one may employ either friabletissues, such as a suspension culture of cells or embryogenic callus oralternatively one may transform immature embryos or other organizedtissue directly. In this technique, one would partially degrade the cellwalls of the chosen cells by exposing them to pectin-degrading enzymes(pectolyases) or mechanically wound tissues in a controlled manner.

A particularly efficient method for delivering transforming DNA segmentsto plant cells is microprojectile bombardment. In this method, particlesare coated with nucleic acids and delivered into cells by a propellingforce. Exemplary particles include those which may be comprised oftungsten, platinum, and preferably, gold. For the bombardment, cells insuspension are concentrated on filters or solid culture medium.Alternatively, immature embryos or other target cells may be arranged onsolid culture medium. The cells to be bombarded are positioned at anappropriate distance below the macroprojectile stopping plate. Anillustrative embodiment of a method for delivering DNA into plant cellsby acceleration is the Biolistics Particle Delivery System, which may beused to propel particles coated with DNA or cells through a screen, suchas a stainless steel or Nytex screen, onto a surface covered with targetlettuce cells. The screen disperses the particles so that they are notdelivered to the recipient cells in large aggregates. It is believedthat a screen intervening between the projectile apparatus and the cellsto be bombarded reduces the size of projectiles aggregate and maycontribute to a higher frequency of transformation by reducing thedamage inflicted on the recipient cells by projectiles that are toolarge. Microprojectile bombardment techniques are widely applicable, andmay be used to transform virtually any plant species, including a plantof lettuce variety 41-CR2537 RZ.

Agrobacterium-mediated transfer is another widely applicable system forintroducing gene loci into plant cells. An advantage of the technique isthat DNA may be introduced into whole plant tissues, thereby bypassingthe need for regeneration of an intact plant from a protoplast.Agrobacterium transformation vectors are capable of replication in E.coli as well as Agrobacterium, allowing for convenient manipulations.Moreover, advances in vectors for Agrobacterium-mediated gene transferhave improved the arrangement of genes and restriction sites in thevectors to facilitate the construction of vectors capable of expressingvarious polypeptide coding genes. The vectors have convenientmulti-linker regions flanked by a promoter and a polyadenylation sitefor direct expression of inserted polypeptide coding genes.Additionally, Agrobacterium containing both armed and disarmed Ti genesmay be used for transformation. In those plant strains whereAgrobacterium-mediated transformation is efficient, it is the method ofchoice because of the facile and defined nature of the gene locustransfer. The use of Agrobacterium-mediated plant integrating vectors tointroduce DNA into plant cells, including lettuce plant cells, is wellknown in the art (See, e.g., U.S. Pat. Nos. 7,250,560 and 5,563,055).

Transformation of plant protoplasts also may be achieved using methodsbased on calcium phosphate precipitation, polyethylene glycol treatment,electroporation, and combinations of these treatments.

A number of promoters have utility for plant gene expression for anygene of interest including but not limited to selectable markers,scoreable markers, genes for pest tolerance, disease resistance,nutritional enhancements and any other gene of agronomic interest.Examples of constitutive promoters useful for lettuce plant geneexpression include, but are not limited to, the cauliflower mosaic virus(CaMV) P-35S promoter, a tandemly duplicated version of the CaMV 35Spromoter, the enhanced 35S promoter (P-e35S), the nopaline synthasepromoter, the octopine synthase promoter, the figwort mosaic virus(P-FMV) promoter (see U.S. Pat. No. 5,378,619), an enhanced version ofthe FMV promoter (P-eFMV) where the promoter sequence of P-FMV isduplicated in tandem, the cauliflower mosaic virus 19S promoter, asugarcane bacilliform virus promoter, a commelina yellow mottle viruspromoter, the promoter for the thylakoid membrane proteins (psaD, psaF,psaE, PC, FNR, atpC, atpD, cab, rbcS) (see U.S. Pat. No. 7,161,061), theCAB-1 promoter (see U.S. Pat. No. 7,663,027), the promoter from maizeprolamin seed storage protein (see U.S. Pat. No. 7,119,255), and otherplant DNA virus promoters known to express in plant cells. A variety ofplant gene promoters that are regulated in response to environmental,hormonal, chemical, and/or developmental signals may be used forexpression of an operably linked gene in plant cells, includingpromoters regulated by (1) heat, (2) light (e.g., pea rbcS-3A promoter,maize rbcS promoter, or chlorophyll a/b-binding protein promoter), (3)hormones, such as abscisic acid, (4) wounding (e.g., wunl, or (5)chemicals such as methyl jasmonate, salicylic acid, or Safener. It mayalso be advantageous to employ organ-specific promoters.

Exemplary nucleic acids which may be introduced to the lettuce varietyof this invention include, for example, DNA sequences or genes fromanother species, or even genes or sequences which originate with or arepresent in lettuce species, but are incorporated into recipient cells bygenetic engineering methods rather than classical reproduction orbreeding techniques. However, the term “exogenous” is also intended torefer to genes that are not normally present in the cell beingtransformed, or perhaps simply not present in the form, structure, etc.,as found in the transforming DNA segment or gene, or genes which arenormally present and that one desires to express in a manner thatdiffers from the natural expression pattern, e.g., to over-express.Thus, the term “exogenous” gene or DNA is intended to refer to any geneor DNA segment that is introduced into a recipient cell, regardless ofwhether a similar gene may already be present in such a cell. The typeof DNA included in the exogenous DNA may include DNA which is alreadypresent in the plant cell, DNA from another plant, DNA from a differentorganism, or a DNA generated externally, such as a DNA sequencecontaining an antisense message of a gene, or a DNA sequence encoding asynthetic or modified version of a gene.

Many hundreds if not thousands of different genes are known and couldpotentially be introduced into a plant of lettuce variety 41-CR2537 RZ.Non-limiting examples of particular genes and corresponding phenotypesone may choose to introduce into a lettuce plant include one or moregenes for insect tolerance, pest tolerance such as genes for fungaldisease control, herbicide tolerance, and genes for quality improvementssuch as yield, nutritional enhancements, environmental or stresstolerances, or any desirable changes in plant physiology, growth,development, morphology or plant product(s).

Alternatively, the DNA coding sequences may affect these phenotypes byencoding a non-translatable RNA molecule that causes the targetedinhibition of expression of an endogenous gene, for example viaantisense- or cosuppression-mediated mechanisms. The RNA could also be acatalytic RNA molecule (i.e., a ribozyme) engineered to cleave a desiredendogenous mRNA product. Thus, any gene which produces a protein or mRNAwhich expresses a phenotype or morphology change of interest is usefulfor the practice of the present invention. (See also U.S. Pat. No.7,576,262, “Modified gene-silencing RNA and uses thereof.”)

U.S. Pat. Nos. 7,230,158, 7,122,720, 7,081,363, 6,734,341, 6,503,732,6,392,121, 6,087,560, 5,981,181, 5,977,060, 5,608,146, 5,516,667, eachof which, and all documents cited therein are hereby incorporated hereinby reference, consistent with the above INCORPORATION BY REFERENCEsection, are additionally cited as examples of U.S. Patents that mayconcern transformed lettuce and/or methods of transforming lettuce orlettuce plant cells, and techniques from these US Patents, as well aspromoters, vectors, etc., may be employed in the practice of thisinvention to introduce exogenous nucleic acid sequence(s) into a plantof lettuce variety 41-CR2537 RZ (or cells thereof), and exemplify someexogenous nucleic acid sequence(s) which may be introduced into a plantof lettuce variety 41-CR2537 RZ (or cells thereof) of the invention, aswell as techniques, promoters, vectors etc., to thereby obtain furtherplants of lettuce variety 41-CR2537 RZ, plant parts and cells, seeds,other propagation material harvestable parts of these plants, etc. ofthe invention, e.g. tissue culture, including a cell or protoplast, suchas an embryo, meristem, cotyledon, pollen, leaf, anther, root, root tip,pistil, flower, seed or stalk.

The invention further relates to propagation material for producingplants of the invention. Such propagation material may comprise interalia seeds of the claimed plant and parts of the plant that are involvedin sexual reproduction. Such parts are for example selected from thegroup consisting of seeds, microspores, pollen, ovaries, ovules, embryosacs and egg cells. In addition, the invention relates to propagationmaterial which may comprise parts of the plant that are suitable forvegetative reproduction, for example cuttings, roots, stems, cells,protoplasts.

According to a further aspect thereof the propagation material of theinvention may comprise a tissue culture of the claimed plant. The tissueculture may comprise regenerable cells. Such tissue culture may bederived from leaves, pollen, embryos, cotyledon, hypocotyls,meristematic cells, roots, root tips, anthers, flowers, seeds and stems.(See generally U.S. Pat. No. 7,041,876 on lettuce being recognized as aplant that may be regenerated from cultured cells or tissue).

Also, the invention comprehends methods for producing a seed of a“41-CR2537 RZ”-derived lettuce plant which may comprise (a) crossing aplant of lettuce variety 41-CR2537 RZ, a sample of seed of which havingbeen deposited under NCIMB Accession No. 44003, with a second lettuceplant, and (b) whereby seed of a 41-CR2537 RZ-derived lettuce plantform. Such a method may further comprise (c) crossing a plant grown from41-CR2537 RZ-derived lettuce seed with itself or with a second lettuceplant to yield additional 41-CR2537 RZ-derived lettuce seed, (d) growingthe additional 41-CR2537 RZ-derived lettuce seed of step (c) to yieldadditional 41-CR2537 RZ-derived lettuce plants, and (e) repeating thecrossing and growing of steps (c) and (d) for an additional 3-10generations to further generate 41-CR2537 RZ-derived lettuce plants.

The invention further relates to the above methods that may furthercomprise selecting at steps b), d), and e), a 41-CR2537 RZ-derivedlettuce plant, exhibiting one or more or all of the physiological andmorphological characteristics of lettuce variety 41-CR2537 RZ, a sampleof seed of said variety having been deposited under NCIMB accession No.44003, and other selected traits.

In particular, the invention relates to methods for producing a seed ofa 41-CR2537 RZ-derived lettuce plant which may comprise (a) crossing aplant of lettuce variety 41-CR2537 RZ, a sample of seed of which havingbeen deposited under NCIMB Accession No. 44003, with a second lettuceplant and (b) whereby seed of a 41-CR2537 RZ-derived lettuce plantforms, wherein such a method may further comprise (c) crossing a plantgrown from 41-CR2537 RZ-derived lettuce seed with itself or with asecond lettuce plant to yield additional 41-CR2537 RZ-derived lettuceseed, (d) growing the additional 41-CR2537 RZ-derived lettuce seed ofstep (c) to yield additional 41-CR2537 RZ-derived lettuce plants andselecting plants exhibiting one or more or all of the physiological andmorphological characteristics of lettuce variety 41-CR2537 RZ, and (e)repeating the crossing and growing of steps (c) and (d) for anadditional 3-10 generations to further generate 41-CR2537 RZ-derivedlettuce plants that exhibit one or more or all of the physiological andmorphological characteristics of lettuce variety 41-CR2537 RZ.

The invention additionally provides a method of introducing at least onenew trait into a plant of lettuce variety 41-CR2537 RZ which maycomprise: (a) crossing a plant of lettuce variety 41-CR2537 RZ, a sampleof seed of which having been deposited under NCIMB Accession No. 44003,with a second lettuce plant that may comprise at least one new trait toproduce progeny seed; (b) harvesting and planting the progeny seed toproduce at least one progeny plant of a subsequent generation, whereinthe progeny plant may comprise the at least one new trait; (c) crossingthe selected progeny plant with a plant of lettuce variety 41-CR2537 RZ,to produce backcross progeny seed; (d) harvesting and planting thebackcross progeny seed to produce a backcross progeny plant, (e)repeating steps (c) and (d) for at least three additional generations toproduce backcross progeny that may comprise the at least one new traitand all of the physiological and morphological characteristics of aplant of lettuce variety 41-CR2537 RZ, when grown in the sameenvironmental conditions. The invention, of course, includes a lettuceplant produced by this method.

Backcrossing may also be used to improve an inbred plant. Backcrossingtransfers a specific desirable trait from one inbred or non-inbredsource to an inbred that lacks that trait. This may be accomplished, forexample, by first crossing a superior inbred (A) (recurrent parent) to adonor inbred (non-recurrent parent), which carries the appropriate locusor loci for the trait in question. The progeny of this cross are thenmated back to the superior recurrent parent (A) followed by selection inthe resultant progeny for the desired trait to be transferred from thenon-recurrent parent. After five or more backcross generations withselection for the desired trait, the progeny are heterozygous for locicontrolling the characteristic being transferred, but are like thesuperior parent for most or almost all other loci. The last backcrossgeneration would be selfed to give pure breeding progeny for the traitbeing transferred. When a plant of lettuce variety 41-CR2537 RZ, asample of seed of which having been deposited under NCIMB Accession No.44003, is used in backcrossing, offspring retaining one or more or allof the physiological and morphological characteristics of lettucevariety 41-CR2537 RZ are progeny within the ambit of the invention.Backcrossing methods may be used with the present invention to improveor introduce a characteristic into a plant of the invention, being aplant of lettuce variety 41-CR2537 RZ. See, e.g., U.S. Pat. No.7,705,206 (incorporated herein by reference consistent with the aboveINCORPORATION BY REFERENCE section), for a general discussion relatingto backcrossing.

The invention further involves a method of determining the genotype of aplant of lettuce variety 41-CR2537 RZ, a sample of seed of which hasbeen deposited under NCIMB Accession No. 44003, or a first generationprogeny thereof, which may comprise obtaining a sample of nucleic acidsfrom said plant and detecting in said nucleic acids a plurality ofpolymorphisms. This method may additionally comprise the step of storingthe results of detecting the plurality of polymorphisms on a computerreadable medium. The plurality of polymorphisms are indicative of and/orgive rise to the expression of the physiological and morphologicalcharacteristics of lettuce variety 41-CR2537 RZ.

There are various ways of obtaining genotype data from a nucleic acidsample. Genotype data may be gathered which is specific for certainphenotypic traits (e.g. gene sequences), but also patterns of randomgenetic variation may be obtained to construct a so-called DNAfingerprint. Depending on the technique used a fingerprint may beobtained that is unique for lettuce variety 41-CR2537 RZ. Obtaining aunique DNA fingerprint depends on the genetic variation present in avariety and the sensitivity of the fingerprinting technique. A techniqueknown in the art to provide a good fingerprint profile is called AFLPfingerprinting technique (See generally U.S. Pat. No. 5,874,215), butthere are many other marker based techniques, such as RFLP (orRestriction fragment length polymorphism), SSLP (or Simple sequencelength polymorphism), RAPD (or Random amplification of polymorphic DNA)VNTR (or Variable number tandem repeat), Microsatellite polymorphism,SSR (or Simple sequence repeat), STR (or Short tandem repeat), SFP (orSingle feature polymorphism) DArT (or Diversity Arrays Technology), RADmarkers (or Restriction site associated DNA markers) (e.g. Baird et al.PloS One Vol. 3 e3376, 2008; Semagn et al. African Journal ofBiotechnology Vol. 5 number 25 pp. 2540-2568, 29 Dec. 2006). Nowadays,sequence-based methods are utilizing Single Nucleotide Polymorphisms(SNPs) that are randomly distributed across genomes, as a common toolfor genotyping (e.g. Elshire et al. PloS One Vol. 6: e19379, 2011;Poland et al. PloS One Vol. 7: e32253; Truong et al. PLoS One Vol. 7number 5: e37565, 2012).

With any of the aforementioned genotyping techniques, polymorphisms maybe detected when the genotype and/or sequence of the plant of interestis compared to the genotype and/or sequence of one or more referenceplants. As used herein, the genotype and/or sequence of a referenceplant may be derived from, but is not limited to, any one of thefollowing: parental lines, closely related plant varieties or species,complete genome sequence of a related plant variety or species, or thede novo assembled genome sequence of one or more related plant varietiesor species. For example, it is possible to detect polymorphisms for thecharacteristic of Bremia resistance by comparing the genotype and/or thesequence of lettuce variety 41-CR2537 RZ with the genotype and/or thesequence of one or more reference plants. The reference plant(s) usedfor comparison in this example may for example be, but is not limitedto, the comparison variety Chicarita R Z.

The polymorphism revealed by these techniques may be used to establishlinks between genotype and phenotype. The polymorphisms may thus be usedto predict or identify certain phenotypic characteristics, individuals,or even species. The polymorphisms are generally called markers. It iscommon practice for the skilled artisan to apply molecular DNAtechniques for generating polymorphisms and creating markers.

The polymorphisms of this invention may be provided in a variety ofmediums to facilitate use, e.g. a database or computer readable medium,which may also contain descriptive annotations in a form that allows askilled artisan to examine or query the polymorphisms and obtain usefulinformation.

As used herein “database” refers to any representation of retrievablecollected data including computer files such as text files, databasefiles, spreadsheet files and image files, printed tabulations andgraphical representations and combinations of digital and image datacollections. In a preferred aspect of the invention, “database” refersto a memory system that may store computer searchable information.

As used herein, “computer readable media” refers to any medium that maybe read and accessed directly by a computer. Such media include, but arenot limited to: magnetic storage media, such as floppy discs, hard disc,storage medium and magnetic tape; optical storage media such as CD-ROM;electrical storage media such as RAM, DRAM, SRAM, SDRAM, ROM; and PROMs(EPROM, EEPROM, Flash EPROM), and hybrids of these categories such asmagnetic/optical storage media. A skilled artisan may readily appreciatehow any of the presently known computer readable mediums may be used tocreate a manufacture which may comprise computer readable medium havingrecorded thereon a polymorphism of the present invention.

As used herein, “recorded” refers to the result of a process for storinginformation in a retrievable database or computer readable medium. Forinstance, a skilled artisan may readily adopt any of the presently knownmethods for recording information on computer readable medium togenerate media which may comprise the polymorphisms of the presentinvention. A variety of data storage structures are available to askilled artisan for creating a computer readable medium where the choiceof the data storage structure will generally be based on the meanschosen to access the stored information. In addition, a variety of dataprocessor programs and formats may be used to store the polymorphisms ofthe present invention on computer readable medium.

The present invention further provides systems, particularlycomputer-based systems, which contain the polymorphisms describedherein. Such systems are designed to identify the polymorphisms of thisinvention. As used herein, “a computer-based system” refers to thehardware, software and memory used to analyze the polymorphisms. Askilled artisan may readily appreciate that any one of the currentlyavailable computer-based system are suitable for use in the presentinvention.

Lettuce leaves are sold in packaged form, including without limitationas pre-packaged lettuce salad or as lettuce heads. Mention is made ofU.S. Pat. No. 5,523,136, incorporated herein by reference consistentwith the above INCORPORATION BY REFERENCE section, which providespackaging film, and packages from such packaging film, including suchpackaging containing leafy produce, and methods for making and usingsuch packaging film and packages, which are suitable for use with thelettuce leaves of the invention. Thus, the invention comprehends the useof and methods for making and using the leaves of the lettuce plant ofthe invention, as well as leaves of lettuce plants derived from theinvention. The invention further relates to a container which maycomprise one or more plants of the invention, or one or more lettuceplants derived from a plant of the invention, in a growth substrate forharvest of leaves from the plant in a domestic environment. This way theconsumer may pick very fresh leaves for use in salads. More generally,the invention includes one or more plants of the invention or one ormore plants derived from lettuce of the invention, wherein the plant isin a ready-to-harvest condition, including with the consumer picking hisown, and further including a container which may comprise one or more ofthese plants.

The invention is further described by the following numbered paragraphs:

-   -   1. A seed of lettuce variety 41-CR2537 RZ, a sample of seed of        said variety having been deposited under NCIMB accession No.        44003.    -   2. A lettuce plant grown from the seed of paragraph 1.    -   3. A lettuce plant, or a part thereof, having all the        physiological and morphological characteristics of the lettuce        plant of paragraph 2.    -   4. A part of the lettuce plant of paragraph 2, wherein said part        comprises a microspore, pollen, ovary, ovule, embryo sac, egg        cell, cutting, root, stem, cell or protoplast.    -   5. A tissue culture of regenerable cells or protoplasts from the        lettuce plant of paragraph 2.    -   6. The tissue culture as paragraphed in paragraph 5, wherein        said cells or protoplasts of the tissue culture are derived from        a tissue comprising a leaf, pollen, embryo, cotyledon,        hypocotyl, meristematic cell, root, root tip, anther, flower,        seed or stem.    -   7. A lettuce plant regenerated from the tissue culture of        paragraph 5 or 6, wherein the regenerated plant expresses all of        the physiological and morphological characteristics of lettuce        variety 41-CR2537 RZ, a sample of seed of said variety having        been deposited under NCIMB accession No. 44003.    -   8. A method of vegetatively propagating a plant of lettuce        variety 41-CR2537 RZ comprising (a) collecting tissue capable of        being propagated from a lettuce plant of paragraph 2, (b)        cultivating the tissue to obtain proliferated shoots and rooting        the proliferated shoots to obtain rooted plantlets, and (c)        optionally growing plants from the rooted plantlets.    -   9. A method for producing a progeny plant of lettuce variety        41-CR2537 RZ, comprising crossing a lettuce plant of paragraph 2        with itself or with another lettuce plant, harvesting the        resultant seed, and growing said seed.    -   10. A progeny plant produced by the method of paragraph 9,        wherein said progeny exhibits all the morphological and        physiological characteristics of the lettuce variety designated        41-CR2537 RZ, a sample of seed of said variety having been        deposited under NCIMB accession No. 44003.    -   11. The progeny plant of paragraph 10, wherein said progeny        plant is modified in one or more other characteristics.    -   12. A lettuce plant of paragraph 2 further comprising a        transgene.    -   13. The plant of paragraph 12, wherein the transgene is        introduced via transformation.    -   14. A method for producing a modified lettuce plant comprising        mutagenizing the seed of paragraph 1 and growing said seed.    -   15. A method for producing a modified lettuce plant comprising        mutagenizing the plant of any one of paragraphs 2, 3 or 7.    -   16. A method for producing a modified lettuce plant comprising        mutagenizing the part of plant of any one of paragraphs 3 or 4.    -   17. A method for producing a modified lettuce plant comprising        mutagenizing the tissue culture of any one of paragraphs 5 or 6.    -   18. A method of producing a lettuce seed comprising crossing a        male parent lettuce plant with a female parent lettuce plant and        harvesting the resultant lettuce seed, wherein said male parent        lettuce plant or said female parent lettuce plant is the lettuce        plant of paragraph 2.    -   19. An F1 lettuce seed produced by the method of paragraph 18.    -   20. A lettuce plant produced by growing the seed of paragraph        19.    -   21. A method for producing a seed of a 41-CR2537 RZ-derived        lettuce plant comprising (a) crossing a plant of lettuce variety        41-CR2537 RZ, a sample of seed of which having been deposited        under NCIMB Accession No. 44003, with a second lettuce plant,        and (b) whereby seed of a 41-CR2537 RZ-derived lettuce plant        forms.    -   22. The method of paragraph 21 further comprising (c) crossing a        plant grown from 41-CR2537 RZ-derived lettuce seed with itself        or with a second lettuce plant to yield additional 41-CR2537        RZ-derived lettuce seed, (d) growing the additional 41-CR2537        RZ-derived lettuce seed of step (c) to yield additional        41-CR2537 RZ-derived lettuce plants, and (e) repeating the        crossing and growing of steps (c) and (d) for an additional 3-10        generations to generate further 41-CR2537 RZ-derived lettuce        plants, and (f) whereby seed of a 41-CR2537 RZ-derived lettuce        plant forms.    -   23. A method of introducing at least one new trait into a plant        of lettuce variety 41-CR2537 RZ comprising: (a) crossing a plant        of lettuce variety 41-CR2537 RZ, a sample of seed of which        having been deposited under NCIMB Accession No. 44003, with a        second lettuce plant that comprises at least one new trait to        produce progeny seed, (b) harvesting and planting the progeny        seed to produce at least one progeny plant of a subsequent        generation, wherein the progeny plant comprises the at least one        new trait, (c) crossing the progeny plant with a plant of        lettuce variety 41-CR2537 RZ to produce backcross progeny        seed, (d) harvesting and planting the backcross progeny seed to        produce a backcross progeny plant, and (e) repeating steps (c)        and (d) for at least three additional generations to produce a        lettuce plant of variety 41-CR2537 RZ comprising at least one        new trait and all of the physiological and morphological        characteristics of a plant of lettuce variety 41-CR2537 RZ, when        grown in the same environmental conditions.    -   24. The lettuce plant produced by the method of paragraph 23,        wherein the plant comprises the at least one new trait and        otherwise all of the physiological and morphological        characteristics of a lettuce plant of lettuce variety 41-CR2537        RZ.    -   25. A method for producing lettuce leaves as a food product        comprising sowing the seed of paragraph 1 and growing the seed        into a harvestable lettuce plant and harvesting the head or        leaves of said plant, optionally processing and/or packaging the        head or the leaves.    -   26. A container comprising one or more lettuce plants of        paragraph 2 for harvest of leaves.

Having thus described in detail preferred embodiments of the presentinvention, it is to be understood that the invention is not to belimited to particular details set forth in the above description as manyapparent variations thereof are possible without departing from thespirit or scope of the present invention.

What is claimed is:
 1. A seed of lettuce variety 41-CR2537 RZ, a sampleof seed of said variety having been deposited under NCIMB accession No.44003.
 2. A lettuce plant grown from the seed of claim
 1. 3. A lettuceplant, or a part thereof, having all the physiological and morphologicalcharacteristics of the lettuce plant of claim
 2. 4. A part of thelettuce plant of claim 2, wherein said part comprises a microspore,pollen, ovary, ovule, embryo sac, egg cell, cutting, root, stem, cell orprotoplast.
 5. A tissue culture of regenerable cells or protoplasts fromthe lettuce plant of claim
 2. 6. The tissue culture as claimed in claim5, wherein said cells or protoplasts of the tissue culture are derivedfrom a tissue comprising a leaf, pollen, embryo, cotyledon, hypocotyl,meristematic cell, root, root tip, anther, flower, seed or stem.
 7. Alettuce plant regenerated from the tissue culture of claim 5, whereinthe regenerated plant expresses all of the physiological andmorphological characteristics of lettuce variety 41-CR2537 RZ, a sampleof seed of said variety having been deposited under NCIMB accession No.44003.
 8. A method of vegetatively propagating a plant of lettucevariety 41-CR2537 RZ, a sample of seed of said variety having beendeposited under NCIMB 44003, comprising (a) collecting tissue capable ofbeing propagated from a lettuce plant of claim 2, (b) cultivating thetissue to obtain proliferated shoots and rooting the proliferated shootsto obtain rooted plantlets, and (c) optionally growing plants from therooted plantlets.
 9. A method for producing a progeny plant of lettucevariety 41-CR2537 RZ, a sample of seed of said variety having beendeposited under NCIMB 44003, comprising crossing a lettuce plant ofclaim 2 with itself or with another lettuce plant, harvesting theresultant seed, and growing said seed.
 10. A progeny plant produced bythe method of claim 9, wherein said progeny exhibits all themorphological and physiological characteristics of the lettuce varietydesignated 41-CR2537 RZ, a sample of seed of said variety having beendeposited under NCIMB accession No.
 44003. 11. The progeny plant asclaimed in claim 10, wherein said progeny plant is modified in one ormore other characteristics.
 12. A lettuce plant grown from a seed oflettuce variety 41-CR2537 RZ, a sample of seed of said variety havingbeen deposited under NCIMB Accession No. 44003, further comprising atransgene.
 13. The plant as claimed in claim 12, wherein the transgeneis introduced via transformation.
 14. A method for producing a modifiedlettuce plant comprising mutagenizing the seed of claim 1 and growingsaid seed.
 15. A method for producing a modified lettuce plantcomprising mutagenizing the plant of any one of claim 2, 3 or
 7. 16. Amethod for producing a modified lettuce plant comprising mutagenizingthe part of plant of any one of claim 3 or
 4. 17. A method for producinga modified lettuce plant comprising mutagenizing the tissue culture ofclaim
 5. 18. A method of producing a lettuce seed comprising crossing amale parent lettuce plant with a female parent lettuce plant andharvesting the resultant lettuce seed, wherein said male parent lettuceplant or said female parent lettuce plant is the lettuce plant of claim2.
 19. An F1 lettuce seed produced by the method of claim
 18. 20. Alettuce plant produced by growing the seed of claim
 19. 21. A method forproducing a seed of a 41-CR2537 RZ-derived lettuce plant comprising (a)crossing a plant of lettuce variety 41-CR2537 RZ, a sample of seed ofwhich having been deposited under NCIMB Accession No. 44003, with asecond lettuce plant, and (b) whereby seed of a 41-CR2537 RZ-derivedlettuce plant forms.
 22. The method of claim 21 further comprising (c)crossing a plant grown from 41-CR2537 RZ-derived lettuce seed withitself or with a second lettuce plant to yield additional 41-CR2537RZ-derived lettuce seed, (d) growing the additional 41-CR2537 RZ-derivedlettuce seed of step (c) to yield additional 41-CR2537 RZ-derivedlettuce plants, and (e) repeating the crossing and growing of steps (c)and (d) for an additional 3-10 generations to generate further 41-CR2537RZ-derived lettuce plants, and (f) whereby seed of a 41-CR2537RZ-derived lettuce plant forms.
 23. A method of introducing at least onenew trait into a plant of lettuce variety 41-CR2537 RZ comprising: (a)crossing a plant of lettuce variety 41-CR2537 RZ, a sample of seed ofwhich having been deposited under NCIMB Accession No. 44003, with asecond lettuce plant that comprises at least one new trait to produceprogeny seed, (b) harvesting and planting the progeny seed to produce atleast one progeny plant of a subsequent generation, wherein the progenyplant comprises the at least one new trait, (c) crossing the progenyplant with a plant of lettuce variety 41-CR2537 RZ to produce backcrossprogeny seed, (d) harvesting and planting the backcross progeny seed toproduce a backcross progeny plant, and (e) repeating steps (c) and (d)for at least three additional generations to produce a lettuce plant ofvariety 41-CR2537 RZ comprising at least one new trait and all of thephysiological and morphological characteristics of a plant of lettucevariety 41-CR2537 RZ, when grown in the same environmental conditions.24. A lettuce plant produced by the method of claim 23, wherein theplant comprises the at least one new trait and otherwise all of thephysiological and morphological characteristics of a lettuce plant oflettuce variety 41-CR2537 RZ.
 25. A method for producing lettuce leavesas a food product comprising sowing the seed of claim 1 and growing theseed into a harvestable lettuce plant and harvesting the head or leavesof said plant, optionally processing and/or packaging the head or theleaves.
 26. A container comprising one or more lettuce plants of claim 2for harvest of leaves.
 27. The lettuce plant of claim 2, which is aplant grown from seed having been deposited under NCIMB Accession No.44003.